The invention relates to a fluid friction clutch for a cooling fan of an internal combustion engine.
From Fed. German Patent Application No. 3,246,783 a fluid friction clutch for a cooling fan of an internal combustion engine is known in which a substantially U-shaped holder for a bimetallic element is fitted on the front of a housing enclosing the driven rotor so as to form shear gaps. The bimetallic element is a component of a regulating device which controls the shear fluid level in the working gap in dependence upon temperature. In the known fluid friction clutch the bimetallic element has a substantially rectangular configuration and is inserted in the region of its short sides into openings of the holder. It is resiliently held in the openings by the relatively slight initial stress force of a valve element arranged in the interior of the housing, which valve element is in connection with the bimetallic element through a thrust piece displaceably passing through the front of the housing. The manner of fastening has the advantage that the bimetallic element can easily be fitted and also replaced. However it has the disadvantage that in the case of heavy vibrations of the internal combustion engine the zones with which the bimetallic element is seated in the retaining fitting are knocked out, so that the bimetallic element can slip out of the retaining fitting due to unintended contact and the cooling fan loses its temperature-regulating properties.
The main concern of the invention is to avoid the above disadvantages and in a manner of simple design to secure the bimetallic element to the front of the housing, namely in such a way that it can be subjected without problem to even heavy vibrations.